1. Field of the Invention
One embodiment of the present invention relates to an object, a method, or a manufacturing method. In addition, one embodiment of the present invention relates to a process, a machine, manufacture, or a composition of matter. In particular, one embodiment of the present invention relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a memory device, a driving method thereof, or a manufacturing method thereof. In particular, one embodiment of the present invention relates to a structure of a storage battery and a method for manufacturing the storage battery. In particular, one embodiment of the present invention relates to a negative electrode active material of a storage battery.
Note that in this specification, the power storage unit refers to all components and devices having a function of storing power.
2. Description of the Related Art
Examples of the storage battery include a nickel-metal hydride battery, a lead-acid battery, and a lithium-ion secondary battery.
Such secondary batteries are used as power sources in portable information terminals typified by mobile phones. In particular, lithium-ion secondary batteries have been actively developed because increased capacity and reduced size can be achieved.
In the lithium-ion secondary batteries, a graphite material is typically used as a negative electrode active material; as another material with high capacity, for example, silicon, tin, and oxides thereof are disclosed in Patent Document 1.